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IRLinker: avoid quadratic behavior #157045

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Merged
merged 2 commits into from
Sep 5, 2025
Merged

IRLinker: avoid quadratic behavior #157045

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008d698
[𝘀𝗽𝗿] initial version
vitalybuka Sep 5, 2025
f622be2
copilot review
vitalybuka Sep 5, 2025
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15 changes: 14 additions & 1 deletion llvm/lib/Linker/IRMover.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,8 @@

#include "llvm/Linker/IRMover.h"
#include "LinkDiagnosticInfo.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/IR/AutoUpgrade.h"
Expand Down Expand Up @@ -290,6 +292,9 @@ class IRLinker {
Module &DstM;
std::unique_ptr<Module> SrcM;

// Lookup table to optimize IRMover::linkNamedMDNodes().
DenseMap<StringRef, DenseSet<MDNode *>> NamedMDNodes;

/// See IRMover::move().
IRMover::LazyCallback AddLazyFor;

Expand Down Expand Up @@ -1132,12 +1137,20 @@ void IRLinker::linkNamedMDNodes() {
continue;

NamedMDNode *DestNMD = DstM.getOrInsertNamedMetadata(NMD.getName());

auto &Inserted = NamedMDNodes[DestNMD->getName()];
if (Inserted.empty()) {
// Must be the first module, copy everything from DestNMD.
Inserted.insert(DestNMD->operands().begin(), DestNMD->operands().end());
}

// Add Src elements into Dest node.
for (const MDNode *Op : NMD.operands()) {
MDNode *MD = Mapper.mapMDNode(*Op);
if (!is_contained(DestNMD->operands(), MD))
if (Inserted.insert(MD).second)
DestNMD->addOperand(MD);
}
assert(Inserted.size() == DestNMD->getNumOperands());
}
}

Expand Down